Recently, highly-active supported transition metal compound catalyst combinations based upon the use of magnesium compounds have become available for the commercial production of polyethylene. For example, U.S. Pat. No. 3,901,863 to Solvay and Cie teaches polymerization of ethylene and its mixtures with, for example, an alkylaluminum compound promoter and a solid catalyst component made from a non-halide containing magnesium alkoxide, a non-halide containing titanium alkoxide and an alkylaluminum halide. Also, U.S. Pat. No. 3,644,318 teaches reaction of selected TiX.sub.n (OR).sub.4-n compounds, where n is 1 to 4, X is Cl or Br, and R is an alkyl group, with Mg(OH).sub.2 to form a co-catalyst to be used with certain organometallic compounds including aluminum alkyls as promoters for the polymerization of ethylene or its mixtures. Further, U.S. Pat. No. 3,900,454 teaches treatment of certain inorganic compounds including magnesium hydroxide with, for example, AlCl.sub.3, and thereafter, treatment with certain transition metal compounds including Ti (IV) alkoxides and chloroalkoxides to form a co-catalyst which is then promoted with certain organometallic compounds including aluminum alkyls for use in suspension polymerization of alpha-olefins including ethylene. However, these catalysts are either of lower than desirable polymer yields, or when highly active, in the sense of producing sufficiently high polymer yields so that no separation of catalyst residues need be carried out in finishing the polymer, the polymer molecular weight distribution is relatively narrow.
Now, new catalyst combinations have been found which can have the high activities of the best of new generation supported and promoted transition metal catalysts and can produce polyethylenes having a reasonable range of molecular weight distributions as represented by MF.sub.10 /MF.sub.1 values.